196 THE REPRODUCTIVE ORGANS OF KUKENTHALIA BOREALIS. 



unexplained. Such a fact is, for instance, the presence of sexual 

 products, i. e. ova, in the mesoderm. 



Isolated ova have been observed before in the mesoderm of 

 Kukenthcdia, but it has not been made out where they originate. 

 As no gonads, only isolated ova were met with, Michaelsen 

 concluded that the female organs of Kukenihcdia consist of ova 

 diffusely placed in the mesoderm. Michaelsen writes as follows : 

 " Diese Gattung weicht durch den Bau der weiblichen Geschlechts- 

 organe von alien iibrigen Polyzohien, ja, von alien Styeliden 

 iiberhaupt, ab. Ich bezeichnete die Gestaltung desselben als 

 ' dift'us,' da die sich entwickelnden Eizellen an kein bestimmt 

 loka.lisiertes Organ gebunden sind, sondern sich weit zerstreut 

 im Innenkbrper und in den Blutbahneu anderer Organe, so 

 besonders des Darmes, sowie in den jungen Knospen, vor- 

 finden. Der urspriingliche Ort der weiblichen Gonaden ist 

 unbekannt.. ." {1. c. p. 112). 



Though female organs of other structure have now been 

 found, the observation that isolated eggs occur in the mesoderm 

 proves to be right. According to my observation, they are, 

 however, met with less abundantly than has been stated above. 

 As it hardly can be thought that they originate in the above- 

 described ovary, one must suppose that they are produced in 

 the mesoderm, where they occur, though in no special gonads, 

 i. e. non-gonadially. This supposition seems to be verified by 

 my observation of small ovaries or, rather, groups of eggs which 

 are situated in the mesoderm close to the wall of the peribranchial 

 cavity and in the vicinity of bud-rudiments. 



In Kukenthalia, buds occur on both sides of the body ; on the 

 left side they are to be seen in the vicinity of the reproductive 

 organs above described. In the mesoderm of those bud-rudiments 

 eggs have been observed, and even in very small bud-rudiments 

 very large eggs are often visible. In all probability the eggs 

 originate in the parent animal, the generative cells being sup- 

 posed to wander from the latter; but the question is whether 

 they are differentiated in the bud or have wandered at an 

 advanced stage from the parent animal into the bud. But this 

 is a problem which can be decided only after thorough investi- 

 gation of the further development of the non-gonaxlial ova as well 

 as of the formation of the reproductive organs of the bud. 



